"Tennessee is scheduled to electrocute David Miller tonight. Miller is the second inmate in just over a month who has chosen to die by the electric chair in order to avoid the State’s current lethal injection protocol." Sotomayor wrote in her dissent.

"Both so chose even though electrocution can be a dreadful way to die. They did so against the backdrop of credible scientific evidence that lethal injection as currently practiced in Tennessee may well be even worse."

Earlier Thursday, Gov. Bill Haslam announced that he will not stop Miller's execution, either.

“After careful consideration of David Earl Miller’s clemency request, I am declining to intervene in this case,” Haslam said in his statement.

Haslam's decision marked the third time this year the governor has allowed an execution to move forward. Death row inmates Billy Ray Irick and Edmund Zagorski were executed in August and November, respectively.